title: MicroRNA-21 promotes hepatocellular carcinoma HepG2 cell proliferation through repression of mitogen-activated protein kinase-kinase 3.
abstract: BACKGROUND
  microRNA 21 (miR-21) has been demonstrated to be significantly elevated in many types of cancers, including the hepatocellular carcinoma (HCC). In the present study, we investigated the role of miR-21 in HCC by identifying its novel targets, as well as its underlying molecular mechanism.
  
  
  METHODS
  The expression of mitogen-activated protein kinase-kinase 3 (MAP2K3) in human HCC tumor tissues and adjacent non-tumor tissues was determined by immunohistochemistry staining (IHC) analysis. The 3'-untranslated region (3'-UTR) of MAP2K3 combined with miR-21 was experimentally verified by a miRNA luciferase reporter approach. Moreover, the role of miR-21 in regulating HCC cell proliferation was analyzed by an MTT assay infected with miR-21mimics/sponge inhibitor Adenoviral viral vectors.
  
  
  RESULTS
  By immunohistochemistry staining analysis, we found that mitogen-activated protein kinase-kinase 3 (MAP2K3) was strikingly repressed in the human HCC tumor tissues, in comparison with the adjacent non-tumor tissues in clinical settings. More importantly, the repression of MAP2K3 was inversely correlated with the expression of miR-21 in HCC. Further study demonstrated that the MAP2K3 was a novel direct target of miR-21, which was experimentally validated by a miRNA luciferase reporter approach. In HepG2 cells, inhibition of miR-21 expression with an adenoviral miR-21 sponge vector profoundly suppressed cell proliferation by up-regulating MAP2K3 expression at both mRNA and protein levels.
  
  
  CONCLUSIONS
  These results provide a clinical evidence that MAP2K3 may be a tumor repressor gene, and it is a direct target of miR-21 in HCC, indicating an underlying mechanism by which miR-21 is able to directly target MAP2K3 and inhibit its expression during the carcinogenesis of HCC, at both transcriptional and post-translational levels. This study also suggests that targeting miR-21-MAP2K3 pathway may be a promising strategy in the prevention and treatment of HCC.
authors.affiliation: General Hospital of Ningxia Medical University, Yinchuan 750004, China. 599040064@qq.com.
authors.forename: Guangxian
authors.initials: G
authors.lastname: Xu
authors.forename: Yilin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Wei
authors.forename: Wei
authors.initials: W
authors.lastname: Jia
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Ge
authors.forename: Zhaobo
authors.initials: Z
authors.lastname: Zhang
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Liu
mesh_terms: D020413:3' Untranslated Regions; D020029:Base Pairing; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D056945:Hep G2 Cells; D006801:Humans; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism; D048371:MAP Kinase Kinase 3 / Q000235:genetics* / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference
chemical_list: D020413:3' Untranslated Regions; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D048371:MAP Kinase Kinase 3